单项选择题
A.Ray cherished his childhood memories. B.Ray had something urgent to take care of. C.Ray may not have a happy childhood. D.Ray cannot remember his childhood days.
A.close. B.remote. C.tense. D.impossible to tell.
A.Knowledge learning and career building. B.Learning how to solve existing social problems. C.Researching into solutions to current world problems. D.Combining research efforts of teachers and students in learning.